System and methods for wireless drug delivery on command

ABSTRACT

A fully integrated small size implantable sensing device is described, which can include a sensor and an electronic circuit to interface with the sensor and communicate with an external device. Various fabrication methods for the sensing device are described, including provision of wells, created using same fabrication technology as the electronic circuit, to contain electrodes of the sensor and corresponding functionalization chemicals. Such implantable sensing device can be used for a variety of electrochemical measuring applications within a living body as well as actuation by injecting a current into the living body.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Divisional of U.S. patent application Ser.No. 15/216,675 filed on Jul. 21, 2016, which, in turn, claims priorityto U.S. Provisional Application No. 62/195,895 filed on Jul. 23, 2015,and U.S. Provisional Application No. 62/204,825 filed on Aug. 13, 2015,the disclosures of all of which are incorporated herein by reference intheir entirety.

The present application is related to U.S. application Ser. No.15/216,662 entitled “Canary on a Chip: Embedded Sensors withBio-Chemical Interfaces” (Attorney Docket No. P1895-US) filed on Jul.21, 2016, the disclosure of which is incorporated herein by reference inits entirety.

The present application may be related to U.S. Pat. No. 9,006,014entitled “Fabrication of Three-Dimensional High Surface AreaElectrodes”, (Attorney Docket No. P1335-US) issued Apr. 14, 2015, thedisclosure of which is incorporated herein by reference in its entirety.

The present application may be related to US Patent Publication No.2014/0228660 entitled “Miniaturized Implantable Electrochemical SensorDevices”, published Aug. 14, 2014, the disclosure of which isincorporated herein by reference in its entirety.

The present application may be related to U.S. Pat. No. 9,177,933entitled “Three-Dimensional High Surface Area Electrodes”, (AttorneyDocket No. P1335-USD) issued Nov. 3, 2015, the disclosure of which isincorporated herein by reference in its entirety.

The present application may be related to U.S. Pat. No. 9,173,605entitled “Fabrication of Implantable Fully Integrated ElectrochemicalSensors”, (Attorney Docket No. P1335-USCIP) issued Nov. 3, 2015, thedisclosure of which is incorporated herein by reference in its entirety.

STATEMENT OF GOVERNMENT GRANT

This invention was made with government support under Grant No. EB020416awarded by the National Institutes of Health. The government has certainrights in the invention.

TECHNICAL FIELD

The present disclosure relates to design, fabrication and usage ofimplantable fully integrated devices which can be used aselectrochemical sensor devices and/or as drug delivery devices in-vivo.

BACKGROUND

The measurement of biological indicators is of interest for a variety ofmedical disorders. Various systems have been developed to measurebiological indicators from within the living body (in-vivo) of variousanimals (e.g. mammals) via an implantable device. It is now possible tobuild compact devices that can measure metabolites and performelectrophysiology with wireless interfaces that communicate withexternal controllers/data readers. It would be desirable to use suchtechnologies to deliver biochemical molecules with precise control overtheir quantity, location and time.

Existing implantable devices have the potential to create high localtemperatures inside the living body. Often power provided from externalsources results in an increase in local temperature around theimplantable device. Often transmission of information from theimplantable device results in an increase in local temperature aroundthe implantable device. The living body, however, cannot tolerate highinternal temperatures. High internal temperatures often lead to tissuedeath [e.g. reference 5, herein incorporated by reference in itsentirety].

Another issue facing implantable devices is the formation of a foreignbody capsule in the tissue of the living body around the implantabledevice. Fibrogen and other proteins bind to the device surface shortlyafter implantation in a process known as biofouling. Macrophages bind tothe receptors on these proteins releasing growth factor 3 and otherinflammatory cytokines. Procollagen is synthesized and becomescrosslinked after secretion into the extracellular space graduallycontributing to formation of a dense fibrous foreign body capsule. Thedense capsule prevents the implantable device from interfacing with theliving body and thereby often hinders the operation of the implantabledevice [e.g. reference 6, herein incorporated by reference in itsentirety].

These issues have been addressed to some extent by a miniaturizedimplantable electrochemical sensor device disclosed in afore mentionedrelated U.S. Patent Publication No. 2014/0228660, incorporated herein byreference in its entirety. However, such miniaturized implantableelectrochemical sensor is not fully integrated (e.g. monolithicallyintegrated) as some of its elements are glued onto the device.

In particular, fully wireless implants are being considered as thefuture of health care system. These implants can improve the health caresystem in many aspects. The ultra-small scale design of these devicespromises many advantages compared to their macro counterparts. This sizescale is perceived to minimize the foreign body response to an implant.It would also enable easy implantation and explantation procedures.Finally, such implants can minimize the permanent risk of infection andirritation associated with wired systems currently being used, such astranscutaneous continuous glucose monitoring (CGM) systems. In manysituations, CGM system being a relevant example, a remotely poweredimplanted sensor can monitor levels of signals of interest and transmitdata to an external receiver/controller avoiding risks associated withsuch wired implants. To allow for reliable power delivery as well asminimizing foreign body response, both the sensor's size and powerdissipation can be minimized. To date, implantable devices that can beused as miniaturized drug delivery devices have not been reported. Itfollows that the present disclosure provides methods and devices whichcan be used to fabricate miniature size implantable devices forapplications related to controlled delivery of biochemical moleculeswhich in some cases can also be coupled with measurement of body fluids,not limited to measurement in a specific environment, and which can beused for a broad range of applications, such as the described “Canary ona Chip” application.

SUMMARY

Solid State electrochemical sensors and actuators at Micro/Nano scalehave gained lots of interest in recent years. Detailed design of suchsensors and actuators using micro/nano technologies can involve manysystem level design issues which need to be addressed together to get anoptimal response for a particular application. In some cases, specialdesign/fabrication/manufacturing techniques can be used so as to allowthese devices to be part of a completely integrated system. The presentapplication discloses such techniques for exemplary cases of implantableintegrated systems, which cases should not be construed as limiting thescope of the present teachings. It is understood that a person skilledin the art can use these same techniques fordesign/fabrication/manufacturing of other types of integrated solidstate electrochemical sensors and actuators using micro and/or nanotechnologies. Such implantable integrated systems can allow minimallyinvasive micro-sensors to monitor, in-vivo, response of cells tospecific analytes, and further allow triggering of therapeutic agentsstored in micro-chambers via integrated actuators.

According to one embodiment the present disclosure, a method forfabricating a miniaturized implantable device is presented, the methodcomprising: fabricating an electronic system by monolithicallyintegrating the electronic system on a first face of a substrate, theelectronic system comprising an energy storage element adapted to becharged through a wireless communication link; fabricating a coil bymonolithically integrating the coil on the first face of the substrate,the coil being configured to provide the wireless communication link;and fixating at least one hermetic package, containing a liquid payload,on the first surface of the substrate, a portion of the hermetic packagebeing positioned above the coil, wherein the energy storage element isconfigured to provide energy to rupture a seal of the hermetic package,thereby dispensing the liquid payload.

According to a second embodiment of the present disclosure, anintegrated miniaturized implantable device is presented, comprising: asubstrate for monolithic integration comprising a plurality of metallayers separated via a plurality of insulating layers; a monolithicallyintegrated electronic system comprising an energy storage elementadapted to be charged through a wireless communication; a monolithicallyintegrated coil configured to provide the wireless communication link;and a hermetic package, containing a liquid payload, fixated on thesubstrate, a portion of the hermetic package being positioned above thecoil, wherein during operation of the implantable device, the electronicsystem is configured to: communicate with an external device over thewireless communication link provided by the coil, extract power for theminiaturized implantable device from the wireless communication link,charge the energy storage element based on the extracted power, andenergize an actuator via the energy storage element to rupture a seal ofthe hermetic package.

Further aspects of the disclosure are shown in the specification,drawings and claims of the present application.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated into and constitute apart of this specification, illustrate one or more embodiments of thepresent disclosure and, together with the description of exampleembodiments, serve to explain the principles and implementations of thedisclosure.

FIGS. 1A and 1B illustrate exemplary geometries of electrodes used for asensor of an integrated implantable device according to embodiments ofthe present disclosure.

FIG. 2 illustrates an exemplary embodiment of a patterned electrodesurface.

FIGS. 3A and 3B illustrate exemplary geometries of sensors used for theintegrated implantable device according to embodiments of the presentdisclosure.

FIGS. 4A and 4B illustrate two sensors whose electrodes are coveredusing two different deposition methods.

FIG. 5 shows a well of the integrated implantable device created using aCMOS process which can be used to hold an electrode and/orfunctionalization chemistry.

FIG. 6 shows vias within the integrated implantable device which can beused to provide connection between the electrodes and underlyingelectronics.

FIG. 7 shows an exemplary integrated implantable device.

FIGS. 8A and 8B show scanning electron microscope pictures of a surfaceof a platinum (Pt) film and a platinum oxide (PtOx) film respectively.

FIG. 9 shows an exemplary electrochemical oxidation curve (currentversus voltage) of platinum in a sulfuric acid solution.

FIGS. 10A-10D show various graphs representative of open circuit testfor electrode (e.g. reference electrode RE) temporal stability andinterference effects in peroxide solution.

FIG. 11 shows an exemplary integrated implantable device according to anembodiment of the present disclosure whose sensor has distributedelectrodes.

FIGS. 12A and 12B show an exemplary sensor of the implantable integrateddevice with distributed electrodes prior to functionalization and afterfunctionalization respectively.

FIG. 13 depicts a block diagram of a system comprising the implantableintegrated device, a corresponding external transmitter/reader and aninterface region between the two.

FIG. 14 depicts a circuit diagram of an exemplary 3-stageself-synchronous full-wave rectifier.

FIG. 15 depicts a circuit diagram of an exemplary linear voltageregulator.

FIG. 16 shows a graph representative of measured rectifier and regulatoroutput voltages at 6 μW load versus transmitted power to the integratedimplantable device at 7 mm separation between the externaltransmitter/reader device and the implanted integrated implantabledevice.

FIG. 17 shows an exemplary embodiment of an acquisition system used inthe implantable integrated device.

FIGS. 18A and 18B show graphs representative of a performance of adual-slope 8 bit ADC (excluding sign bit) used in the acquisition systemdepicted in FIG. 17.

FIG. 19 shows a size of an exemplary implementation of the integratedimplantable device.

FIG. 20 shows a graph representative of a performance of the exemplaryimplementation for detecting glucose concentration and contrasted to aperformance of a commercial potentiostat.

FIG. 21 shows an oscilloscope image representative of variouscommunication sequences between the external transmitter/reader deviceand the integrated implantable device.

FIG. 22 shows a table representative of various performances of theexemplary implementation.

FIG. 23 depicts the block diagram of the system depicted in FIG. 13 withan added actuator unit which allows the system to perform an actuatingtask.

FIG. 24 depicts a block diagram of a system comprising a wirelessimplantable integrated device, a corresponding externaltransmitter/reader and an interface region between the two, where theimplantable integrated device comprises an actuator for dispensing apayload of a delivery module.

FIG. 25 shows a simplified cross section of the wireless implantableintegrated device of FIG. 24.

FIG. 26 shows an exemplary actuator, payload and delivery module of thewireless implantable integrated device of FIG. 25, represented by anelectrochemical cell that facilitates a dissociation reaction of waterinto its constituent elements.

FIG. 27A and FIG. 27B show a two-chamber configuration of the deliverymodule, where an electrochemical reaction can take place in a chambernext to the chamber containing the payload (drug to be delivered).

FIG. 28 shows a simplified top view of a wireless implantable drugdelivery device according to an embodiment of the present disclosurecomprising a dual chamber configuration.

FIG. 29 shows a simplified top view of a wireless implantable drugdelivery device according to an embodiment of the present disclosurecomprising a single chamber configuration.

FIG. 30 depicts the block diagram of the system depicted in FIG. 29 withan added sensor/electrode unit which allows the system to perform asensing task.

FIG. 31 shows a simplified top view of a wireless implantable drugdelivery device according to an embodiment of the present disclosurecomprising multiple chambers.

FIG. 32 shows a simplified rendering of an in-vivo bio-electronic systemaccording to an embodiment of the present disclosure that is protectedby a semi-permeable cell containment barrier.

DETAILED DESCRIPTION

As used herein, a “monolithic substrate” is a substrate upon whichcomponents are monolithically integrated and therefore such componentsare not adhered and/or secured via mechanical means to the substrate. Invarious embodiments according to the present disclosure the monolithicsubstrate can be the result of processing using CMOS technology or otherfabrication technology known to the skilled person. It is understoodthat a monolithic substrate has multiple faces, and at least a firstface and a second face. A first and second face can be distinguishedfrom other faces of the monolithic substrate in that the first andsecond face are larger than the other faces of the monolithic substrate.

As used herein, the term “sensor” can refer to the region of theimplantable device responsible for the detection of a particularbiological indicator. For example, in some embodiments for glucosemonitoring, the sensor interface refers to that region wherein abiological sample (e.g., blood or interstitial fluid) or portionsthereof contacts an enzyme (e.g. glucose oxidase); a reaction of thebiological sample (or portion thereof) results in the formation ofreaction products that allow a determination of the glucose level in thebiological sample. In various embodiments of the present invention, thesensor further comprises a “functionalization layer” as described laterin the present disclosure. In various embodiments of present disclosurethe sensor can be monolithically integrated into the monolithicsubstrate. In various embodiments of the present disclosure themonolithically integrated sensor can be placed on a different face ofthe monolithic substrate from a corresponding signal processing circuit.This can be done in various embodiments by forming for example highsurface electrodes (e.g. patterned electrodes) similarly to the methoddescribed below on a silicon face of the monolithic substrate andinterconnecting them through the monolithic substrate to the other faceof the monolithic substrate comprising the signal processing circuit.More information on sensors and patterned electrodes and constructionmethods thereof can be found, for example, in the referenced U.S. Pat.No. 9,006,014 entitled “Fabrication of Three-Dimensional High SurfaceArea Electrodes”, issued Apr. 14, 2015, herein incorporated by referencein its entirety.

Fully integrated electrochemical sensor devices can be attractive in avariety of applications requiring measurement of different species indifferent environments. For the case of implantable sensingapplications, these devices can detect/provide very selective andsensitive signal as well as ease of integration with signal processingplatforms using, for example, CMOS technology.

According to the various embodiments of the present disclosure presentedin the following sections, full integration of these devices can beachieved by using design methods that takes into account the presence ofthe complete system around the electrochemical sensors. Furthermore,fabrication methods and techniques according to the various embodimentsof the present disclosure used for the integrated devices are compatiblewith the complete system and do not affect the performance of anycorresponding subsystem substantially.

An electrochemical sensor (e.g. a potentiometric/amperometric sensor)can consist of multiple electrodes. Commonly three electrodes are used,a working electrode, a counter electrode and a reference electrode. Thereference electrode can be used to establish a stable potentialreference in a target measurement environment (e.g. a chemical solution,blood, interstitial fluid, etc.)). The working electrode can be used forgenerating an electrical signal (e.g. a current flow) corresponding tosome interface reaction of one or more specie of interest within thetarget measurement environment. The counter electrode, which can be apassive element of a circuit comprising the electrochemical sensor inthe target measurement environment, can generally be used to balance thecurrent of the working electrode. For some systems where very smallsignals are generated, the reference electrode can also act as thecounter electrode and therefore eliminating the need for a thirdelectrode. For some other systems where placement of a referenceelectrode can be difficult, a floating reference-less (electrode) designcan be used. A four or more electrode design can also be used where morethan one working electrodes can be used to measure differential signallevels for better noise immunity or multiple species at a time.

For implantable sensor applications (e.g. humans, mammals) where size ofthe sensor is of importance, the floating reference-less design canresult in smaller device footprint. However, if long term stability ofan implantable sensor is a major design issue, three electrode designwith a dedicated and stable reference electrode can be a more attractivedesign approach.

Micro/Nano scale structuring of integrated electrodes can provide manyuseful features for a variety of applications. Methods for designing andfabricating such integrated electrodes are disclosed by Applicants ofthe present disclosure in the above referenced U.S. Pat. No. 9,006,014entitled “Fabrication of Three-Dimensional High Surface AreaElectrodes”, issued Apr. 14, 2015, herein incorporated by reference inits entirety.

For implantable sensor applications where selectivity of the sensor isdesirable, functionalization of the corresponding electrodes can be auseful technique. Sensors according to the various embodiments of thepresent disclosure are designed to easily incorporate in situfunctionalization (e.g. electrodes can be functionalized afterfabrication/integration within the integrated sensor device). Themicro/nano scale geometry of the sensors coupled with a well structurearound the sensors, as described in the above referenced U.S. Pat. No.9,006,014, issued Apr. 14, 2015, and US Patent Publication No.2014/0228660, published Aug. 14, 2014, which are both incorporatedherein by reference in their entirety, make such functionalizationpossible by retaining the functionalization matrix in its place.

As known to a person skilled in the art, functionalization is a processby which the electrodes of the sensor are covered by a “functionallayer” to provide specificity to a target of interest. The phrase“functional layer” refers to a layer comprising any mechanism (e.g.,enzymatic or non-enzymatic) by which a target of interest can bedetected into an electronic signal for the device. For example,according to some embodiments of the present invention, a functionallayer can contain a gel of glucose oxidase that catalyzes the conversionof glucose to gluconate: Glucose+O₂->Gluconate+H₂O₂. Because for eachglucose molecule converted to gluconate, there is a proportional changein the co-reactant O₂ and the product H₂O₂, one can monitor the currentchange in either the co-reactant or the product to determine glucoseconcentration. In various embodiments of the present disclosure thefunctional layer can comprise a hydrogel (e.g. BSA) loaded with anenzyme (e.g. glucose oxidase). In various alternative embodiments of thepresent disclosure the functional layer can also be a polymer (e.g.polypyridine) loaded with an enzyme (e.g. glucose oxidase).

According to the various embodiments of the present disclosure, methodfor design, fabrication and manufacturing of solid state electrochemicalsystems on very small (Micro/Nano) scale on integrated platform arepresented next. Such solid state electrochemical systems can incorporatesensors using micro and nano scale features, and corresponding signalprocessing circuits designed using, for example, CMOS technology, allintegrated within a millimeter size implantable device. In an exemplaryembodiment according to the present disclosure, such implantable devicecan have a surface area no larger than 1.4 mm×1.4 mm and down to 1.0mm×1.0 mm, and a thickness no larger than 250 μm with nofunctionalization layer chemistry applied, and no larger than 0.5 mmincluding the functionalization layer and a protective layer.Furthermore, the die (e.g. CMOS die used for fabrication) can be furtherthinned down (e.g. from a back side of the die) to about 100 μm (e.g.from 250 μm) to provide an even thinner device, of thickness no largerthan 200 μm and down to about 100 μm with no functionalization layerchemistry applied. In some embodiments functionalization layer chemistrycan have a thickness of about or smaller than 200 μm and the protectivelayer (e.g. packaging, biocompatibility/diffusion limiting gel) can havea thickness of about or smaller than 100 μm. Accordingly, the integratedimplantable device, in its finished state, can have a total size ofabout 1.0 mm×1.0 mm×200 μm to 1.0 mm×1.0 mm×400 μm, depending onrequirement or not of the protective layer and thickness of thefunctionalization layer (e.g. whether or not the functionalization layercan be fully embedded within the later described wells).

Sensor Design

Three electrode based designs, as described in previous sections of thepresent disclosure and known to the person skilled in the art, can bethe common choice for stable performance in long term applications (e.g.expected continuous usage of possibly several months). According to anembodiment of the present disclosure an optional fourth electrode can beused to perform background noise cancellation and/or differentialcalibration. Since design constraints of the implantable integrateddevice can include total available area, according to some embodimentsof the present disclosure the fourth electrode can be used if a decreasein size of the other electrodes such as to compensate for placement ofthe fourth electrode (and corresponding additional signal processingcomponents) does not compromise their performance. Inclusion ofadditional signal processing for a fourth electrode can also increasesize and power consumption of on-chip signal processing circuitry. Thiscan also be taken into account during the design of the implantableintegrated device. Although exemplary cases of three and four electrodesensor designs are mentioned in this section of the present disclosure,the skilled person readily knows that these are mere exemplary in natureas alternative designs using, for example, 2 and more than 4 electrodessensors are also possible given the present teachings.

When the electrochemical sensor is within a target measuring environmentto detect a specie of interest, some current can exist which is causedby sources other than the specie of interest. Such current, which can bereferred to as background current, can be caused by circuit noise,interfering chemicals (e.g. acetaminophen, L-ascorbic acid, etc. in thecase of H₂O₂ based sensors), as well as detected species not produced bya sensing chemistry of the electrochemical sensor (e.g. backgroundlevels of H₂O₂ or O₂). For applications where the background signal ofthe target measurement environment changes rapidly, the use of a fourthelectrode can be beneficial to reduce the effects of such rapid changeson a detected signal. In the case of implantable applications, severityof such effects can depend on whether or not the electrode chemistry canminimize the background changes, such as for example, by blocking outinterfering chemicals such as acetaminophen and L-ascorbic acid. If theelectrode chemistry can minimize the background changes, then threeelectrodes can be sufficient, and if not, a fourth electrode which canbe used for differential measurement can be beneficial.

Once the total area and number of electrodes is established (e.g. aspresented in the previous sections of the present disclosure), accordingto further embodiments of the present disclosure the working electrodesurface area of the electrodes can be established according to a desiredsignal-to-noise ratio from the background signal. This can beestablished via a combination of mathematical modeling, computersimulations and experimental results. Once the working electrode surfacearea is established, the counter electrode is designed to have a surfacearea multiple times larger (e.g. 3-20 times larger) than the workingelectrode so as to avoid any loading of the sensor signal. The referenceelectrode can be designed to have a surface area comparable to theworking electrode in size, to put it at close proximity to most of theworking electrode so as to minimize iR drop between the two electrodes(e.g. due to the uncompensated resistance between the two electrodes).Finally, the reference electrode can be placed closest to the workingelectrode rather than to counter electrode.

According to further embodiments of the present disclosure, saidconstraints related to number of electrodes and total available surfacearea for the electrodes can be fulfilled by different geometries of theelectrodes. A geometrical approach can be used to optimize the designiteratively. Two exemplary design geometries of sensors and associatedelectrodes are shown in FIGS. 1A and 1B. Both sensors depicted in FIGS.1A and 1B can cover a same surface and can have three electrodes, suchas, for example, a working electrode (WE), a reference electrode (RE),and a counter electrode (CE) respectively identified as (110, 115, 120)in FIGS. 1A and 1B.

The sensors shown in FIGS. 1A and 1B can have planar electrodes.According to some embodiments and depending upon specific applicationsand requirements, one or more of the electrodes of the sensors can bepatterned. Patterned electrodes can be utilized to enhance performanceas they can possess an increased effective surface area relative toplanar (e.g. non-patterned) electrodes, as described, for example, inthe referenced U.S. Pat. No. 9,006,014 entitled “Fabrication ofThree-Dimensional High Surface Area Electrodes”, issued Apr. 14, 2015,herein incorporated by reference in its entirety. An example of apatterned electrode is shown in FIG. 2.

In exemplary embodiments according to the present disclosure the designof the patterned electrodes can be made using commercial software. PMMA950 A4 can be used to achieve clean lift-off while still achieving adesired resolution. The resist can be spun at 4000 rpm for 1 minutefollowed by a 180° C. bake for 5 minutes. A dose of 1200 μc/cm2 can beused to write the pattern in a Leica EBPG5000+ optical system. Patternscan be developed in 1:3 solution of MIBK and IPA for 20 seconds followedby a deionized water rinse. Afterwards, a 50 nm alumina mask can besputter coated in a Temescal TES BJD-1800 DC reactive sputter system bydepositing aluminum in oxygen plasma for 5 minutes. Lastly, mask liftoffcan be performed in dicholoromethane in an ultrasonic bath for 2minutes. Successful patterning was confirmed by the applicants ofpresent disclosure via optical microscopy (not shown).

In exemplary embodiments according to the present disclosure patterningcan next be performed with a MA-N 2403 resist. Pillars can be fabricatedusing both dry plasma (Cl2:BCl3) as well as wet etchants (e.g. TMAH) toetch away parts of the metal pad using, for example, a UNAXIS RIEmachine. For the dry plasma (Cl2:BCl3) etch, the temperature can be setto 25 degrees Celsius and RIE power to 120 watts. Flow rate for Cl2 canbe set to 4 SCCM and the flow rate of BCl3 can be set to 20 SCCM. Forthe wet TMAH etch, the surface can be submerged in a liquid at roomtemperature for 10 minutes. Success can be seen in the dimensions anduniformity of the formed structure.

According to a further embodiment of the present disclosure, suchsensors, either planar or patterned (e.g. comprising planar/patternedelectrodes), can also be fabricated on the front side of the ICsubstrate. In an exemplary embodiment according to the presentdisclosure construction methods for metal structures available in CMOStechnology can be used to fabricate such planar and/or patternedsensors. These can be combined (e.g. integrated) with the constructionsteps related to the electronic IC, including connections between thesensor and the IC. In yet another exemplary embodiment according to thepresent disclosure, an exposed silicon area on the front surface can beused to fabricate such planar and/or patterned sensors during apost-processing step (e.g. after the CMOS processing step). According toyet another exemplary embodiment according to the present disclosure,planar and/or patterned sensors can be fabricated on a top metal layerusing same fabrication technology (e.g. CMOS) as the requiredelectronics, while the required electronics (e.g. IC) can be designedunder the top metal layer (e.g. either fully or partially) to reduce theoverall die area. In the case of the latter exemplary embodiment,spacing between the electrodes can be utilized to allow, for example,optical/RF waves, to reach optical/RF elements (e.g. integratedphotovoltaic devices, RF antennae) which can be placed on a lower levelbelow a level corresponding to the top metal layer. Such waves can beused to transmit/receive signals from/to the integrated device'selectronic circuit. The person skilled in the art will know how to usesuch teachings according to the present disclosure fortransmission/reception of other types of signals through regions of thetop metal layer.

With further reference to a combined method of fabricating the sensorsand the underlying electronics, according to some embodiments of thepresent disclosure, sensor design can be integrated within the design ofthe underlying electronic circuitry, using, for example, CMOSfabrication technology. Using such fabrication technology, exemplarysensor (e.g. two, three or higher electrodes) geometries can includerectangular as well as polygonal integrated sensors on a correspondingCMOS chip, as depicted in FIG. 3A (rectangular sensor) and FIG. 3B(polygonal sensor). According to some exemplary embodiments of thepresent disclosure, such integrated sensors can be fabricated during aCMOS processing phase using a top metal layer in a stack of metal layers(e.g. of a CMOS substrate) used in the CMOS fabrication. As known to aperson skilled in the art, CMOS fabrication process can use a pluralityof metal layers for interconnection. Such layers can be stacked on topof each other with insulator layers (e.g. oxide layers) separating them.Top metal layer as used herein is referred to the top most metal layerin the stack of metal layers, which generally can have a top insulatorlayer (e.g. top most insulator layer) above it. Therefore, a lower metallayer can be a metal layer of the stack below the top metal layer. Inalternative embodiments according to the present disclosure, theintegrated sensors can be fabricated during a CMOS processing phaseusing a lower metal which can be later exposed using further etching oftop insulating layers (e.g. oxide layers which can separate a top metallayer from the lower metal layer). Latter method using a lower metal canprovide a deeper well (e.g. for depositing a different metal and/orfunctionalization chemistry, later described) for corresponding sensorselectrodes and therefore can allow for increasing the thickness offunctionalization chemistry on top of the electrodes, although accordingto some embodiments of the present disclosure such well may compriseportion of and not all the functionalization layer.

In some cases common metals available in the processing phase of theunderlying electronics (e.g. CMOS) are not very suitable forelectrochemical sensing applications. For example, CMOS processingtypically can use Al, Cu, Al/Cu metal alloys which can be undesirablefor electrochemical sensing applications. It follows that according tofurther embodiments of the present disclosure such undesirable metalscan be covered (e.g. using electron beam deposition) or replaced (e.g.using etching followed by deposition) with more suitable metals forelectrochemical sensing during a corresponding post-processing step.These more suitable metals can be, for example, noble metals (e.g.platinum-based (Pt) metals, Iridium-based (Ir) metals, gold-based (Au)metals). More information about this post-processing step is provided inlater sections of the present disclosure.

Integration of the electrodes into the chip (e.g. fabricated via CMOSprocess) used for the electronics of the sensor device and thecorresponding post-processing method as per the described embodiments ofthe present disclosure can provide advantages which the person skilledin the art can appreciate. For example, such integrated sensor designcan avoid the need to bond separate sensor dies to the electronic chip(e.g. CMOS) which in can therefore reduce a corresponding system sizeand eliminate noise due to extra wiring required between the electronicchip and a non-integrated sensor. Such integrated electrodes can befabricated on a same side (e.g. referred to as top side) of the die asthe underlying electronic circuitry is fabricated (e.g. via CMOSprocess).

With further reference to the post-processing step for fabrication ofthe integrated sensors, corresponding desirable metal deposition methodscan include electron beam deposition for planar coatings or sputteringfor more conformal coatings of patterned electrodes. Other methods knownto the skilled person, such as thermal evaporation, can also be usedduring this post-processing step. FIGS. 4A and 4B depict integrated CMOSsensors (e.g. electrodes) where corresponding electrodes are coveredwith desirable metals using two different deposition methods; FIG. 4Adepicts an integrated CMOS sensor deposited via electron beam depositionmethod and FIG. 4B depicts an integrated CMOS sensor deposited viasputtering method.

In exemplary embodiments according to the present disclosure, metaldeposition can be performed by sputtering which can also provideconformal coatings. First high density Argon plasma of 20 mTorr can beused to increase the isotropy of the deposition. A 5 nm Ti adhesionlayer can be DC sputtered and then 50 nm or 100 nm Au or Pt films can beDC sputtered. A special stage can be used which can tilt the sample withrespect to the incoming metal atoms at angles up to 90° C. Secondly, thestage can rotate at speeds up to 120 r.p.m. A combination of tilt androtation along with optimization of plasma parameters (high pressure,around 20 mTorr) resulted in very uniformly controlled conformalsidewalls, as witnessed by the applicants of the present disclosure.

According to further embodiments of the present disclosure, electrodemetals created via the chip manufacturing process, such as CMOS, can beetched (e.g. completely) so as to create wells that can be used todeposit more suitable metals and to provide for thicker electrodes ifdesirable. In combination, such wells can also be used to hold all orportion of the functionalization chemistry. One such well created byetching a top metal is shown in FIG. 5, which depicts an angled view ofa sidewall of the well, which in the exemplary case of FIG. 5, has ameasured depth of 3.78 μm. Exemplary well thickness can be about 4 μmalthough thicker wells in the range of 5 μm-6 μm can be obtained byetching lower layers of the substrate. It should be noted that thevarious embodiments according to the present disclosure can be providedeither with or without the wells.

According to further embodiments of the present disclosure and withfurther reference to the etching of a top metal layer for deposition ofa desirable electrode metal material, although the top metal (e.g.aluminum, copper, etc.) is etched (e.g. completely etched away),electrical connections of the deposited metal (e.g. Pt) can be made withthe rest of the CMOS circuit through vias created through acorresponding CMOS processing which can be made of a different material(e.g. tungsten) and hence are not etched during the etching of the topmetal layer (e.g. aluminum, copper, etc.). These vias, which can be madeof a different conducting material, are shown in FIG. 6. The personskilled in the art readily understands that vias can be vertical metalconnectors that connect the underlying circuitry to the top metal layerthat is exposed (e.g. and etched away), as shown in FIG. 6. The 4 by 4array of circles depicted in FIG. 6 are the vias that penetrate througha lower insulating layer (e.g. base on the well) and showing at aboundary of the etched area.

Usage of inherent structures created during the electronic chipfabrication as provided by the teachings of the present disclosure,using for example a CMOS process, in a post-processing step (e.g.creation of wells) as previously described and for functionalization ofthe electrodes, can result in a sensor which is fully integrated withthe rest of the system (e.g. comprising electronics, vias, etc.). Inturn, this can result in a higher manufacturing yield and reliability ofthe sensor and the system as a whole.

According to a further embodiment of the present disclosure, suchsensors, either planar or patterned (e.g. comprising planar/patternedelectrodes), can also be fabricated on the front side of the ICsubstrate. In an exemplary embodiment according to the presentdisclosure construction methods for metal structures available in CMOStechnology can be used to fabricate such planar and/or patternedsensors. These can be combined with the construction steps related tothe electronic IC, including connections between the sensor and the IC.In yet another exemplary embodiment according to the present disclosure,an exposed silicon area on the front surface can be used to fabricatesuch planar and/or patterned sensors during a post-processing step (e.g.after the CMOS processing step). According to yet another exemplaryembodiment according to the present disclosure, planar and/or patternedsensors can be fabricated on a top metal layer, while the requiredelectronics (e.g. IC) can be designed under the top metal layer (e.g.either fully or partially) to reduce the overall die area. In the caseof the latter exemplary embodiment, spacing between the electrodes canbe utilized to allow, for example, optical/RF waves, to reach optical/RFelements (e.g. integrated photovoltaic devices, RF antennae) which canbe placed on a lower level below a level corresponding to the top metallayer. Such waves can be used to transmit/receive signals from/to theintegrated device's electronic circuit. The person skilled in the artwill know how to use such teachings according to the present disclosurefor transmission/reception of other types of signals through regions ofthe top metal layer.

According to an embodiment of the present disclosure the backside of anelectronic integrated circuit (IC) substrate (e.g. fabricated via CMOStechnology) can be used for fabricating such sensors (e.g.monolithically) which can then be connected to corresponding controlcircuits (e.g. signal processing) of the IC fabricated on the front sideof the substrates using conducting traces, either through the substrateor from a side. FIG. 7 shows an exemplary embodiment according to thepresent disclosure where a sensor fabricated on the back side of asubstrate is connected to an electronic IC fabricated on the front sideof the substrate through vias created in the substrate.

According to further embodiments of the present disclosure such sensorscan be fabricated separately from the corresponding electronic IC andbonded to the CMOS substrate of the IC at a later stage. Such bondingcan be performed at a chip scale (e.g. one chip at a time) or at a waferscale (e.g. several chips at a time). Different types of wafer bondingschemes known to a person skilled in the art can be used for thispurpose.

The material constraints, such as metals/conductors used for theelectrodes, can depend on a specific application. Noble metals and noblemetal oxides can be used as electrode material for their stability.Platinum based metals can be used for their activity towards most of themetabolic species directly, such as in the case of H₂O₂ and O₂, orindirectly via an intermediate chemistry such as in the case ofenzymatic sensing or polymer based sensing or sensing whilefunctionalized using other chemistry. For example, oxygen, glucosedetection can be done using such platinum based metals. Gold electrodescan be used for nucleic acid detection due to the ease of binding ofgold through thiol bonds. Reference electrodes using, for example,Ag/AgCl material can be fabricated using known solid state fabricationmethods which can readily support such material. Same material can beused for counter electrode as well. According to some embodiments of thepresent disclosure the working electrode and the counter electrode canbe fabricated using a same metal and therefore simplify fabricationprocess. Choice of metal material for the counter electrode can be basedon ability to sustain current so as to not limit working electrodecurrent (e.g. size) and chemical compatibility of the metal material.Noble metals can satisfy both such requirements and less inert noblemetals can be desirable in some circumstances (e.g. platinum can be moredesirable over gold).

According to various embodiments of the present disclosure, thereference electrode material can be either Ag/AgCl based or noble metals(e.g. platinum (Pt), iridium (Ir), gold (Au), etc.) based materials. Agcan be deposited during a post-processing step of the integrated deviceand can be chlorinated using either chlorine plasma or by dipping it ina chloride solution (e.g. hydrochloric acid), or electrochemically in asolution containing chloride ions (e.g. hydrochloric acid). Pt based orother noble metals based reference electrodes can help avoid the use ofother materials (e.g. silver Ag) and hence can make the post-processingstep simpler. Since Pt itself is sensitive to pH and peroxideinterference, in some cases, such as glucose sensing, it can be unstablefor usage as a reference electrode. However, coating such referenceelectrode with a suitable insulating layer can increase its stability.For example, a somewhat inert layer of Platinum Oxide (PtOx) can be usedto make a combined Pt/PtOx reference electrode. According to anexemplary embodiment of the present disclosure a Pt/PtOx working and/orcounter electrodes can be fabricated by oxidizing a Pt layer of theelectrodes electrochemically or by depositing oxidized platinum on theelectrodes. The former method can eliminate a need for an additionaldeposition step which can be beneficial in reducing manufacturing cost,time and complexity. Using a same material for both the working and thecounter electrodes can be desirable since it can avoid the need ofhaving an additional material (e.g. Ag) and/or using other types ofelectrodes (e.g. hydrogen-based, mercury-based, etc.) which may needspecial post-processing and may also be toxic (e.g. Ag, AgCl). It shouldbe noted that Pt based reference electrodes can be used in harshconditions where reference electrodes made of Ag/AgCl may not befeasible, although simple Pt may be better in such extreme conditions.Since Pt is a noble and very inert material, it is not easy to oxidizeeven with strong oxidizers such as hydrogen peroxide. Applicants of thepresent disclosure have attempted oxidation of Pt electrodes (e.g.reference electrode fabricated on the integrated sensor) using strongoxygen plasma as well as using strong oxidizing agents (e.g. sulfuricacid) along with high electrochemical voltages applied to the Pt. Oxygenplasma exposure showed some effect on the Pt surface and correspondingelectron diffraction x-ray studies showed some oxygen as part of a filmon the surface of the Pt. The films were subsequently heated to releaseany oxygen physically adsorbed in the films. Attempts in determining thechemical nature of the oxide film were inconclusive. Nonetheless, theresulting electrochemical stability suggested that the film (e.g. asformed on the surface of a Pt reference electrode upon oxidation underoxygen plasma and heating to remove absorbed oxygen while not affectingoperation of the underlying electronic system) had become a betterreference electrode material than bare Pt. SEM's (e.g. via scanningelectron microscope) of such films are shown in FIGS. 8A and 8B, formerfigure depicting a Pt based film and latter figure a PtOx based filmobtained via the mentioned steps of oxygen plasma exposure followed byheating.

According to further embodiments of the present disclosure noblemetal/noble metal oxide electrodes can be used as reference or workingelectrodes depending on a desired application. Noble metal/noble metaloxide electrodes can be fabricated using cleanroom procedures, e.g. viadeposition under oxygen plasma, or chemically, such as withelectrochemical oxidation in a mixture of strong oxidizers which caninclude sulfuric acid and hydrogen peroxide (e.g. FIG. 9). Applicants ofthe present disclosure have developed special operating parameters forsaid deposition techniques such as usage of such techniques fordeposition of noble material on the integrated electrodes do not damagethe underlying circuitry (e.g. fabricated for example via CMOS methods).FIG. 9 shows an exemplary electrochemical oxidation curve (currentversus voltage) of platinum in a sulfuric acid solution (e.g. 0.1M(molar concentration in phosphate buffered saline (PBS)) used forfabrication of noble metal/noble metal oxide integrated electrodes.FIGS. 10A-10D show various graphs representative of open circuit testfor electrode (e.g. reference electrode RE) temporal stability andinterference effects in peroxide solution. These are summarized in thetable below.

Temporal Stability Peroxide Interference Electrode Material (voltagechange) (voltage change) Ag 15 mV 120 mV  Pt 30 mV 60 mV Ag/AgCl  5 mV 3 mV Pt/PtOx 20 mV 10 mV

According to an exemplary embodiment of the present disclosure, adeposition under oxygen plasma technique can be used to produce a noblemetal/noble metal oxide reference electrode on the sensor. Thiseliminates the need to use a wet electrochemical post processing step.According to an alternative embodiment of the present disclosure anelectrochemical oxidation technique can be used in order to produce ametal/metal oxide electrode, such as Pt/PtOx. Such electrochemicaloxidation technique can be done in a mixture of sulfuric acid (e.g.strong oxidizer) at a concentration of 1-2 M and hydrogen peroxide (e.g.strong oxidizer) at a concentration of 0.5-2 M dissolved in phosphatebuffer saline (which can provide a source of chloride ions for Ag/AgClreference electrode stability). The Pt electrode can then be oxidized bysubjecting it to high oxidative and low reductive potentials repeatedly(e.g. alternating). The high oxidative potential can oxidize the Ptlayer of the electrode while the low reductive potential can polish theoxide layer for increased stability of the layer. In one exemplaryembodiment the high oxidative potential can be 2.5 V with respect toAg/AgCl reference potential and the low reductive potential can be 0.5 Vwith respect to the same reference potential. In an alternativeembodiment of the present disclosure, the electrode can be oxidizedgalvanostatically by subjecting in to determined oxidative and reductivecurrents repeatedly, with same effects as mentioned with respect to thehigh oxidative and low reductive potentials. Those skilled in the artcan readily extend these teachings according to the present disclosureand use in other electrochemical techniques. Stability of electrodesfabricated using such techniques were characterized by the applicants ofthe present disclosure by measuring open circuit potential of thePt/PtOx electrode with respect to a Ag/AgCl reference electrode overtime, as depicted in FIGS. 10A-10D and above table. The electrochemicaloxidation technique herein presented can be performed at roomtemperature (e.g. 24 degrees Celsius) as well as any temperature rangebetween 10 degrees and 100 degrees Celsius (e.g. solution in liquidform). A higher temperature can provide for a quicker oxidation of themetal.

Interface properties (e.g. surface) of the electrodes can be controlledby control of material deposition onto the electrodes to promote adesired reaction. This can increase the reaction rate as well astransduction of the signal from the functionalization chemistry.Furthermore, this can be optimized to stabilize the immobilizationmatrix (e.g. hydrogel) for long term applications.

According to some exemplary embodiments of the present disclosure, theelectrode surfaces can be formed or modified in order to promote desiredreactions. Some deposition techniques and rates can provide a roughersurface that can increase surface area and thus current. Grain formationcan be encouraged or discouraged in the metal layers, as grainboundaries can allow the solution to penetrate through the top metallayer to some extent and interact with the lower layers, which can bedesirable, for instance in Ag/AgCl reference electrode, or undesirable,as in the Pt electrodes with less inert metals (such as titanium (Ti),tungsten (W), copper (Cu), etc.) underneath.

According to further embodiments of the present disclosure, the surfaceof the electrode can also be made more hydrophilic, for instance byapplying a high voltage plasma (e.g. a technique colloquially referredto as just zapping), or by using an oxygen plasma either during or afterdeposition. This can enable hydrophilic substances to adhere better onthe electrode surface, such as, for example, an immobilization matrix(e.g. a gel containing reaction enzymes which can immobilize the enzymeand prevent it from leaching into the analyte (e.g. blood orinterstitial fluid)). The person skilled in the art readily appreciatesthe various teachings according to the present disclosure which allowflexibility in electrode surface characteristics as to provide ahydrophobic or a hydrophilic electrode in an integrated electrochemicaldevice.

In some cases it can be desirable for an integrated system (e.g.integrated electrochemical sensor) to have some special functionalpatterns such as, for example, through holes for fluid flow. It followsthat according to an embodiment of the present disclosure the electrodesare designed around such functional patterns in a distributed manner.Distributed electrodes, as depicted in FIG. 11, can provide an increasein signal quality (e.g. of the interface reaction) due to thedistributed nature of a corresponding analyte solution. Design ofdistributed electrodes can be done utilizing fractal mathematics tooptimize signal to noise ratio while considering the distributed natureof the analyte solution. In the exemplary embodiment according to thepresent disclosure depicted in FIG. 11, the distributed electrodes areshown on the back side of an integrated device so as to utilize theentire available die area, and are connected to the electronics on thefront through corresponding vias and connections (not shown).Alternative embodiments can be provided where the distributed electrodesare designed on the front side of the integrated system (e.g. same asthe electronic IC).

It should be noted that although the exemplary distributed electrodesconfiguration depicted in FIG. 11 shows electrode components of asubstantial same geometry (e.g. length and width), the teachingsaccording to the present disclosure allow the person skilled in the artto adapt corresponding distributed electrodes geometries to particulardesign and functional constraints of the integrated device. For example,the electrodes can be designed to be long and narrow rectangles for acase where a long rectangular device is desired, or can be square for acase where a square device is desired. Same design rules as presented inthe previous sections of the present disclosure for design ofnon-distributed electrodes can be applied to the design of distributedelectrodes as well.

Sensor Fabrication:

Fabrication of fully integrated electrochemical devices according to thevarious embodiments of the present disclosure must be performed in amanner to avoid damage to the various underlying system and componentsof the device, such as, for example, the electronic IC which can befabricated using known CMOS related methods, and/or other related systemcomponents. In follows that various fabrication methods according tofurther embodiments of the present disclosure which reduce damage to theunderlying system and components thereof are presented in the followingsections.

For planar sensors, spray-coating based lithography can be used in caseswhere corresponding device dies are small, or cases where acorresponding edge bead (e.g. accumulation of resist at the edge of adie) is significant or cases where a corresponding surface morphologydoes not allow proper spinning of resists. Standard lithographicpatterning can be achieved in other cases. It should be noted that thesurface of the electronic substrates may not be completely planar, andtherefore resists which can provide enough thickness to result in aconformal coating can be used. According to some embodiments of thepresent disclosure, high power/long duration temperature andUltraviolet/e-beam exposure can be avoided during the lithographicpatterning. This can be done, for example, by using resists which canachieve lithographic patterning in short duration with moderate dosages.

For isolation of the sensor with respect to other components of theintegrated device, high temperature and long duration thermal oxidationtechniques, which can damage the underlying electronics, can be avoidedin favor of low-temperature and short duration deposition basedtechniques. Such low-temperature and short duration depositiontechniques can be used to deposit desired isolation materials. Forexample, CVD based techniques instead of thermal oxidation can be usedto isolate portion of the substrate material (e.g. silicon) used forsensor fabrication from substrate material used for the other componentsof the integrated device (e.g. electronics). In general, the variousprocesses and methods according to the various teachings of the presentdisclosure can be performed at temperatures between 10 and 200 degreesCelsius such as not to damage the underlying electronics.

Similarly, low temperature deposition techniques, such as, for example,sputtering and electron beam deposition, can be used to depositdifferent materials desired for fabrication of the sensors. Avoidinghigh temperature thermal deposition during fabrication of the sensorscan in turn reduce damage to the electronic substrate and relatedcomponents.

Aligned Photolithography and electron beam lithography can be used tocreate micro and nano scale structures on the sensor electrodes, forcases where patterned electrodes are desired. Dummy patterns can befabricated during the CMOS fabrication process to act as alignment marksfor fabrication methods of such patterned electrodes. The Lithographicmethods for fabrication of the patterned sensors can be done at a waferscale during the electronics fab (e.g. CMOS) phase or at a die scaleafter the wafers are received from the fab and processed. The waferlevel processing of patterned sensors can decrease overall productioncost of the integrated device and can increase a corresponding yield.

Sensors according to the various embodiments of the present disclosurecan be used in implantable integrated devices. In order to reducecomplexities after implantation, the sensors can be covered withbiocompatible materials. This can be done by depositing suchbiocompatible materials using, for example, vacuum based deposition orsimple dip-coating type methods.

Functionalization

Functionalization of sensors according to the various embodiments of thepresent disclosure can be performed so as to make these sensorsselective to different species. Such functionalization can be doneeither in situ or ex situ. FIG. 12A shows an exemplary sensor withdistributed electrodes prior to functionalization. An exemplaryresulting configuration of the sensor depicted in the FIG. 12A with afunctionalization matrix is shown in FIG. 12B.

In-Situ functionalization can allow for an easily integratable process.For small dies, spotting and dip coating can be used for applying afunctionalization matrix. According to an embodiment of the presentdisclosure, a single step functionalization can be performed by spincoating at wafer level before dicing the final dies. Such single stepfunctionalization can increase uniformity and repeatability performanceof the functionalization.

Well structures according to the various embodiments of the presentdisclosure formed in the CMOS sensor (e.g. during a CMOS post-processingphase) can be advantageously used during the functionalization phase.Individual dies can be functionalized by injecting liquid hydrogelmixture, for instance using a fluid dispensing robot, into wells on theCMOS sensor formed in post-processing. Wafer-scale functionalization canbe performed using a fluid dispensing robot, as well as via spin orspray coating of the wafer, stencil coating, or whole wafer coatingfollowed by stencil protected removal, for instance via oxygen plasma.Using spin or spray coating, leveraging the form factor advantages thewells provide, and protected subtractive gel patterning, are noveltechniques according to the various embodiments of the presentdisclosure that enable cost-effective wafer-scale production for thepresented integrated electrochemical sensors.

Functionalization Versatility

The Chemistry used for functionalization of the integratedelectrochemical sensors according to the teachings of the presentdisclosure can be versatile and hence can lead to a variety ofapplications. Since the underlying CMOS circuitry can bemodified/adapted to perform a variety of electrochemical sensing tasks,and since each sensing task can be functionalized with an array orvariety of chemistries, the applications of the sensors according to thepresent teachings can be innumerable. Some exemplary applications arepresented below.

The sensor can also be functionalized with any oxidoreductase to detectelectron transfer, or peroxide concentration, or oxygen concentration,or any other change resulting from enzyme interaction with an analyte.For instance lactate oxidase can be used to sense lactate. Applicants ofthe present disclosure have used glucose oxidase, glucose dehydrogenase,and their mixtures with horseradish peroxidase in order to achieveglucose sensing. For the case of enzymatic sensing, following examplesillustrate this point further.

For renal sensors, following enzymes can be used instead of glucoseoxidase: uricase (uric acid), urease, ascorbate oxidase, and sarcosineoxidase (e.g. creatinine)

For liver function testing, following enzymes can be used: alcoholoxidase and malate dehydrogenase.

Other notable enzymes can include glucoamylase, glutamate oxidase andcholesterol dehydrogenase.

For physical stress and similar sensing functions, lactate oxidase canbe used.

Integrated electrochemical sensors according to the various teachings ofthe present disclosure can be used for sensing mechanisms other thanamperometric sensing. For example, such integrated electrochemicaldevices can be used for electrochemical impedance measurement, or evenfor stress sensing using cortisol level (e.g. as a level of cortisolhormone can rise during psychological stress) in people with stressmanagement issues. The person skilled in the art readily appreciates theflexibility provided by the presented integrated electrochemical sensorand can use the present teachings to produce integrated sensors andcorresponding circuitry for specific applications.

Exemplary Case 1: Fully Wireless Implantable Sensing Device

In this section of the present application an exemplary system designcase using the fully integrated electrochemical sensor device presentedin the previous sections of the present application is provided. Theexemplary design according to the various embodiments of the presentdisclosure as presented in this section is a miniaturized fullyimplantable continuous (e.g. real-time and always available) healthmonitoring microsystem on a CMOS platform. The proposed designincorporates electrochemical sensing techniques as presented in theprior sections of the present application using an ultra-low-powerelectronics as the underlying electronics. It can be wirelessly poweredthrough an electromagnetic wireless link and can support bidirectionaldata communication with an external transmitter/reader device (e.g.reader) through the same wireless link. A low-power potentiostat is usedto interface with the on-chip sensor (e.g. electrodes) and an ADC recordthe on-chip sensor readout. Dynamic range of the ADC can be programmablevia wireless configuration data sent to the wireless sensor device.Functionalized integrated electrodes, as per the teachings of thevarious embodiments presented in the previous sections of the presentdisclosure, are used to enable a specific measurement, such as, forexample, glucose level body fluids. Applicants of the present disclosurehave fabricated a prototype of the presented wireless implantablesensing device in CMOS technology and were successful in validating suchdevice for complete wireless operation in a tissue. The sensingcapability of the implanted device was tested using glucose measurementsas an example.

The fully-integrated wireless sensor platform (e.g. system) presentedwherewith, is at reduced size scale (near millimeter scale in largerdimensions) compared to current state-of-the-art systems. Multipleunique features of the presented system allow such reduction in size.First, power transfer and data telemetry is performed using an optimizedintegrated electromagnetic wireless link without using a large sizeantenna. Furthermore, using the various teachings in the previoussections of the present disclosure, the sensor is realized usingminiaturized integrated electrodes acting as an electrochemical sensorafter suitable functionalization. An ultra-low power and ultra-smallscale potentiostat is designed to control the sensor operation. This isfollowed by an ultra-low power and ultra-small ADC which converts theanalog sensor signal into digital domain. The overall power consumptionof the implant is minimized by using ultra low power and minimal numberof components in the electronics as well as by using ultra-low powercommunication link (e.g. modulation scheme) between the implant and anexternal transmitter/reader. The prototype demonstrates the feasibilityof drastically miniaturizing implantable sensing systems which canconceptually enable their application in making clinically accuratemeasurements in many areas. The applicants of the present disclosurehave proved such concept by implementing a CGM type prototype system asimplementation of such system can be challenging as well as useful inthe healthcare industry. The prototype system is fabricated in 0.18 μmCMOS technology but is not limited by this technology in any way. Thesensor is implemented using the top metal in the CMOS process usingpost-processing (e.g. as described in previous sections of the presentdisclosure) thus avoiding the need of bonding external sensors to theelectronics and hence achieving minimal size and power consumption.Therefore, in the prototype system, the sensor and the underlyingelectronics are located on a same face of the integrated device,although according to the teachings of the present disclosure suchsensor can be also placed on a face opposite to the top face.

FIG. 13 shows a block diagram of the wireless implantable sensing deviceaccording to an exemplary embodiment of the present disclosure. Itconsists of integrated electronics to control sensor operation (labelledsensor signal acquisition), a power management system (labelled powermanagement unit) to power the whole system, a transmit system tocommunicate the data to the external transmitter/reader (labelled TXPWM-backscattering 900 MHz), a receive system to receive commands fromthe external system (labelled RX PWM-ASK 900 MHz), an integrated threeelectrodes based electrochemical sensor (labelled WE, RE, CE forworking, reference and counter electrode respectively) and anelectromagnetic wireless link for both power and communication (labelledimplant antenna).

According to an exemplary embodiment of the present disclosure, theelectromagnetic wireless link through which power is provided to theimplantable sensing device and which is also used as a bi-directionalcommunication link, can be an inductive coupling link designed tooperate in the industrial, scientific and medical (ISM) radio band at afrequency close to 900 MHz (e.g. 902-928 MHz), which can be employed inthe exemplary wireless implantable device so as to minimize loss insidetissues [e.g. reference 4, herein incorporated by reference in itsentirety]. The person skilled in the art readily understands that thechoice of the frequency can depend upon many factors and can thereforebe different for different applications. Furthermore, the wireless linkdoes not need to be an inductively coupled link (e.g. near-field) as anRF link with far-field powering and communication can also be used.

At the chosen frequency band, an on-chip resonant system consisting ofan inductor (e.g. L) and capacitor (e.g. C) can be used to resonate withan external LC system at a matching resonant frequency. The on chip coil(e.g. antenna) can be implemented using the top metal (e.g. fabricatedvia CMOS process) or a combination of metal layers depending uponapplication and thickness of metal layers. For instance, a relativelythick top metal layer of thickness about 4 μm to 5 μm may be sufficientfor fabricating the coil, such as the case for the prototype implantabledevice the applicants of the present disclosure fabricated (e.g. topmetal layer about 4.6 μm thick). In other cases such thickness may notbe sufficient or a top metal layer may not have such thickness, andtherefore several metal layers can be stacked to provide a desirablethickness for fabrication of the coil. In a preferred embodiment, for agiven size of the on chip coil (e.g. available surface space), anassociated inductance as well as quality factor can be maximized. Forinductive links, an on-chip capacitor can be used together with theinductor of the on chip coil to create an LC resonant system. In oneexample, the applicants of the present disclosure used a thick top metalavailable in a commercial CMOS process (e.g. TSMC 0.18 μm process) tomake a 4 turn coil which occupies 1.3×1.3 mm². A 400 fF on-chipmetal-insulator-metal (MIM) capacitor (e.g. labelled C in FIG. 13) isused to resonate with the coil at the selected frequency (e.g. close to900 MHz). The person skilled in the art readily appreciates the smallform factor of the LC resonant system presented which can be used towirelessly power the implantable device.

A high frequency signal (e.g. at the selected frequency) that theresonant system receives is converted to DC using an efficientrectifying circuit. For example, in their prototype implementation, theapplicants of the present disclosure used a 3-stage self-synchronousfull-wave rectifier followed by a 400 pF MOS capacitor to filter aresulting ripple, as shown in FIG. 14. Simulation data have shown thatsuch rectifier, as depicted in FIG. 14, can have an efficiency of 60%,as measured by power received by the on-chip LC system to power outputby the rectifier. Based on the rectified output VRECT, a voltagereference (e.g. V_(REF) of FIG. 15) and a linear voltage regulatorcircuit (e.g. FIG. 15) are used to create a stable supply voltage V_(DD)at a desired level for operation of the various subsystems. Such voltagelevel can depend upon factors of the overall design. For the exemplaryprototype system presented herein, a stable 1.2V supply voltage V_(DD)using an efficient voltage reference in conjunction with a referencevoltage generator (e.g. as shown in FIG. 13) is generated. The voltageregulator, as depicted in FIG. 15, is designed to have improvedstability and reduced power consumption. As an example, a capacitor Ccof FIG. 15 is used to introduce a zero in a frequency response plot ofthe voltage regulator circuit and therefore help with the stability ofthe regulator. Filtering is also performed on the regulated voltageV_(DD) to further ensure stability and to reduce high frequency supplynoise. As an example, such filtering can be provided by an on-chip MOScapacitor C_(L) of FIG. 15. For the exemplary prototype system, suchcapacitor value can be 550 pF. A voltage limiter can also be employed soas to avoid excessive voltage at the rectifier output to protect systemintegrity. Although not shown in FIG. 13, such voltage limiter can beprovided at the output of the rectifier. The power supply described inthis section can generate reasonable power with suitable separation(e.g. distance) between the external resonant system and the implanteddevice. As an example, measured rectifier and regulator output voltagesat 6 μW load versus transmitted power at 7 mm separation between theexternal transmitter/reader and the implant (e.g. implanted device) areshown in FIG. 16. The person skilled in the art readily appreciates thelow power consumption system (e.g. 6 μW) presented in this section toperform the power management task of the implantable device.

The sensor signal acquisition system can comprise a readout circuitryincluding a potentiostat to maintain the required redox potentialbetween the working (WE) and reference (RE) electrode while supplyingcurrent through the counter (CE) electrode using a feedback amplifier asshown in FIG. 17. The potentiostat can be employed in differentelectrochemical modes to detect glucose. According to some embodimentsof the present disclosure the potentiostat can work in both amperometryand cyclic voltammetry regime for glucose detection and can support awide range of voltage difference between the working and referenceelectrode while covering a large current range as well. The current fromthe potentiostat is converted into digital domain using an n-bit(excluding the sign bit) dual-slope ADC with an on-chip integratingcapacitor, C_(INT). In order to enable bidirectional current measurement(e.g. communication from the external transmitter/reader to the implantand from the implant to the external transmitter/reader), atrans-impedance amplifier (TIA) with resistive feedback can be employedat the front-end as an interface between the working electrode and thedual-slope ADC, as depicted in FIG. 17. Another on-chip capacitor C₁ canbe used to further reduce TIA noise. The TIA can also prevent injectionof the ADC switching noise into the sensor working electrode.

According to an embodiment of the present disclosure, by using aprogrammable integration time for the ADC, large range (e.g. over 80 dB(20 pA-500 nA)) of sensor current can be measured. An on-chip oscillatorcan provide the clock reference for the ADC. FIGS. 18A and 18B summarizethe performance of the dual-slope 8 bit ADC (excluding sign bit)designed for the prototype system. As depicted in these figures, aneffective number of bits (ENOB) of 7.3 bit at 4 KHz sampling rate isachieved with less than 0.6 least significant bit (LSB) integralnon-linearity (INL). Such acquisition performance according to thepresented exemplary embodiment of the present disclosure demonstratesthat such low power ADC can provide adequate system performance for mosttypes of implants. The person skilled in the art readily appreciates anincreased performance provided by the ultra-low power, flexible,on-the-fly programmable acquisition system which can be used tocalibrate the implantable device at run time (e.g. via programmableintegration time) as these are desirable features for such implantabledevices.

Communication to the exemplary wireless device can be provided viaelectromagnetic links, which can provide both power and data on the samelink. An interrogation signal from an external transmitter/reader device(e.g. reader) can be transmitted to the implant using differentmodulation schemes. According to one exemplary embodiment, pulse-widthmodulation of the actual power signal can be used to conveycommunication data, including the interrogation signal. This allowsusing the same link for both power and communication. For example, onesand zeros can be coded using different pulse widths. In the exemplaryprototype system, ones and zeros are coded using 2 s and 5 s pulsesrespectively. During the reader to implant communication, animplant-specific tag (e.g. address) can be sent to the sensor to wake upthe sensor readout circuitry, as more than one implant can be implantedat a vicinity of one another. Such tag can initiate a data acquisitioncycle of a signal detected by the specific sensor. After the sensorreadout is done via the acquisition system, the output of the ADC can beserialized and transmitted wirelessly to the reader through a low-powermodulation scheme. Such low-power modulation scheme provides a highenough signal to noise ratio at the reader's detecting coil. In anexemplary embodiment according to the present disclosure, data can besent from the sensor device to the reader via pulse-width modulation ofan impedance seen by the detecting coil (e.g. at the reader device)through a switch. This low-power modulation method effectively usesload-shift keying (LSK) modulation scheme in which a change in theimpedance of the coil of the sensor device (e.g. via a switch, asdepicted in FIG. 13) is reflected onto the reader's coil as a varyingimpedance and therefore a transmitted RF signal by the reader device canbe affected (e.g. via backscattering) accordingly. Applicants of thepresent disclosure have used such low-power modulation scheme in thepresented prototype system to send data to the reader at a rate up to200 Kb/s. After each cycle of interrogation, the reader can remainsilent until data from the sensor is received. Correspondingcommunication signal flow is shown in FIG. 21 which is described inlater sections of the present disclosure.

With further reference to the fabrication methods according to thepresent disclosure provided in previous sections, a post-processing stepis performed to fabricate an integrated electrochemical sensor device onthe same chip (e.g. and surface) where the various electronic systems(e.g. per prototype system) are fabricated, which can also eliminate theneed of complex bonding techniques associated with adding a sensor tosuch device. The post-processing can include lithographic deposition ofthin layer (e.g. 100 nm) of Pt on working and counter electrodes andanother thin layer of either Pt or Ag (e.g. 200 nm of Ag) on thereference electrode. If Ag is used for the reference electrode, plasmachlorination can be done to create a top AgCl layer to result in Ag/AgClreference electrode using afore mentioned methods which do not harm theunderlying electronics. The sensor of the prototype device wasfunctionalized in situ with Glucose Oxidase enzyme using Bovine SerumAlbumin (BSA) hydrogel as the immobilization matrix and Glutaraldehydeas the crosslinking agent. Post-processing can further include coveringthe rest of the system (e.g. all except the electrodes) with ahermetically tight biocompatible material so as to immune the operationof the electromagnetic link of the integrated implant from effects dueto operation in fluidic media as well as reduce toxicity issues in thebody due to the implanted device. FIG. 19 shows the prototype systemfabricated according to the various teachings of the present disclosurewhose size is contrasted to a US quarter coin (e.g. 25 US cents). Afirst magnified view shows the 4-turn coil (e.g. shaped like a plurality(e.g. 4) of concentric similar patterns) covering a perimeter region onthe top side of the integrated device with the sensor in the center ofthe device, and a second magnified view shows the three electrodes ofthe sensor, the reference electrode having an Ag/AgCl top layer. Itshould be noted that although a thickness of the prototype system is notshown in FIG. 19, as noted in prior sections of the present disclosure,such thickness can be down to 100 μm and not larger than 500 μm (e.g.0.5 mm).

The functionality of the implanted prototype sensor was validated inglucose measurement over 0-20 mM concentration using amperometry with0.4V potential between the working and reference electrodes. FIG. 20shows the result (e.g. labelled CMOS) along with the reading from acommercial potentiostat (CHI1242B).

Power to the implanted device can be provided via an external device(e.g. reader device). Configuration of such external device can varybased upon requirements and applications. Functionality of such devicecan be provided by an application specific IC or a system with discretecomponents. As an example, an external printed circuit board (PCB) withan LC resonator is used as proof of concept. The resonator is tuned tothe same frequency as the implant resonator thus transferring powerefficiently to it. Using the prototype system in combination with theexternal PCB, 22 dBm of power was transmitted by using a 2×2 cm²external inductor coil on the external PCB, which was separated from theCGM implant by 5 mm of muscle tissue and 5 mm of air. The linkperformance was insensitive for up to +3 mm center-to-centermisalignment between the reader and the implant (e.g. center ofcorresponding coils).

External Transmitter/Reader

The external device acts as a transmitter and a reader and can consistof some commercial components to generate radio frequency signals (e.g.UHF, 900 MHz ISM band, etc.) of a desired frequency and timing, and anexternal coil to couple to the integrated sensor device. It is notedthat according to some embodiments of the present disclosure, a handhelddevice, such as, for example, a cellular phone, fitted with specialsoftware can be used as the transmitter/reader.

According to some embodiments of the present disclosure, the externaldevice can comprise an array of coils (e.g. more than one) that arearranged in a particular pattern. Same electronics can be used tosequentially power each coil and measure a received signal to determinethe position of the sensor based, for example, on a power of thereceived signal. The coil or set of coils with a higher received signalpower can be used for effectively powering and communicating with theintegrated device as described in the previous sections of the presentdisclosure. Such detection algorithm and selection of coils tocommunicate and power the integrated device provides a higher energydensity from the coil(s) and allows achieving good power transferefficiency to the chip while being able to withstand small changes inimplant position with time. The array of coils and correspondingarrangement pattern can be further used to shape a resultantelectro-magnetic (EM) field in order to focus on the implant location,increasing power efficiency and possible implant depth.

According to other embodiments of the present disclosure, the reader andtransmitter functions of the external device can be incorporated innon-dedicated devices, such as personal devices like cell phones,tablets and the like. This can be done by designing the integratedsensor system around frequencies which such non-dedicated devices canoperate upon, and incorporating the reader and transmitter functions(e.g. modulation, demodulation, RF power transmit etc.) in a chipset ofthe non-dedicated device.

FIG. 21 shows communication signals detected between the reader and theimplant which are shaped as pulses of varying length. Actual signal atthe antennae (e.g. RF at 900 MHz ISM frequency band) is modulated bythese pulses. Once the interrogation signal sent during an interrogationsequence is received by the sensor, glucose reading starts within asignal acquisition sequence and the result of the acquisition istransmitted to the reader during a backscattered data sequence in whichdata representing the acquired data is provided the to the reader viamodulation of the impedance of the coil of the integrated sensor. Thetable depicted in FIG. 22 summarizes the performance of the prototypesystem and compares it to state-of-the-art systems as described inreferences [1, 2], both incorporated herein by reference in theirentirety. The prototype system, fabricated using the various embodimentsaccording to the present disclosure, is the smallest reported wirelessCGM system with more than 15 times reduction in area and 60 timesreduction in volume while providing comparable performance to thecurrent state-of-the-art systems. The person skilled in the art readilyappreciates the advantages provided by such integrated device andunderlying fabrication methods, which allow for a small size (e.g. 1mm×1 mm×(100 μm-500 μm)) and low power consumption device while stillproviding adequate performance for one of the most complex sensingscenario of measuring glucose.

Implantation and Removal Methods

The integrated sensing device according to the various embodiments ofthe present disclosure can be implanted in the skin, subcutaneoustissue, intraperitoneal cavity, organs, brain, muscle, or in othertissues. An incision can be made in the body for implantation.Alternatively, an appropriate gauge trocar and/or needle can be used forimplantation of the device. The person skilled in the art readilyappreciates the implantation flexibility provided by the small size ofthe implantable device according to the various embodiments of thepresent disclosure, such as usage of a trocar and/or needle of anappropriate gauge to completely embed the implantable device in thetissue. Removal of such implant can be performed, for example, via asimple incision, or by using a trocar followed by a grabbing instrument.

Actuation

According to a further embodiment of the present disclosure, theintegrated electrochemical sensor according to the teachings of thepresent disclosure can be used for actuation as well. The electrodes ofthe sensor can be used to flow current through a corresponding localenvironment. by forcing a voltage or current across the electrodes. Forsmall sensors which have limited output current capacity, this can bedone in pulsed mode so as to be able to deliver enough current to thelocal environment. A small sensor can have a capacity to provide currentwhich is smaller compared to the one required by the tissue regionintended for actuation. For example, continuous actuation of heartmuscle with less than a microampere of current available for a wirelessintegrated sensor according to the present teachings can be difficult.However, the wireless integrated device can be operated in a pulsed modeto overcome such low current limitation. This can be done by utilizingenergy storing elements (e.g. capacitors) within the wireless integrateddevice to accumulate electrical energy for actuation. Although largersurface area of the electrodes can help increase the current range ofthe electrochemical system, the overall current (e.g. in continuousoperation) is still limited by the wireless power transfer to thesystem. Multiple such devices can be used in synchronization to improveactuation. The advantage of small size and small current (or voltage) isthat very local actuation is possible.

Actuation can be activated by a control logic signal upon receiving aspecific tag sequence that tells the integrated implantable device tobegin actuation along with the relevant parameters (e.g. duration,actuation waveform etc.). Such integrated implantable device configuredto perform actuation is depicted in the block diagram of FIG. 23. Anactuator unit (e.g. Actuator of FIG. 23) allows performing the task ofactuation by injecting current to electrodes (e.g. CE, RE, WE) of thesensor. A switch (e.g. MUX) can allow connection of the electrodes toeither the sensor signal acquisition unit for sensing, or to theactuator unit for actuation. Upon receipt of the actuating tag sequencefrom an external device, a capacitor bank (e.g. uses as an energystoring subsystem), which can reside within the actuator unit, can becharged through the wireless power link. Also, a control logic based onthe tag sequence can connect the electrodes (e.g. working and countervia the switch MUX) to the actuator unit of the implantable integrateddevice. A waveform shaping circuit of the actuator unit can convert theelectrical energy of the capacitor bank to a desired waveform (e.g.voltage, current) signal through the waveform shaping circuit. Thiswaveform signal is then fed to the electrodes which transfer acorresponding energy to nearby tissue (e.g. where device is implanted)for actuation purposes. A waveform signal can be obtained by simplyconnecting the electrodes directly to the capacitor bank (e.g. viaswitch MUX) which causes the capacitor bank to discharge exponentiallybased upon the tissue conductance (e.g. and capacitance value of thebank). Other options for waveform generation can be current limitingcircuits which allow a constant current for the entire actuation period.A multiplexer (e.g. switch) can be used to make sure that both thesensor and the actuator circuits are not connected to the electrodes atthe same time. The person skilled in the art readily appreciates theflexibility provided by exemplary embodiment according to teachings ofthe present disclosure as depicted in FIG. 23 for using the integratedelectrochemical device in both a sensing and an actuating mode. Theactuation can be used for many purposes including, but not limited to,cleaning the electrode surfaces, cleaning the sensor surface,therapeutic actuation of nerves or other tissues (e.g. heart tissue).Multiple of the devices with controlled actuation can allow verycontrolled (e.g. focused) local actuation, owing to the small size ofthe device.

Exemplary Case 2: Fully Wireless Implantable Drug Delivery Device

Based on the above description of a wireless implantable sensing device,a wireless implantable drug delivery device according to a furtherexemplary embodiment of the present disclosure is now presented. Thefunction of drug delivery can be either added to or exchanged with thesensing function of the wireless implantable sensing device discussedabove. According to some embodiments of the present disclosure, suchremote controlled wireless device can be implanted as a hermeticallysealed system in order to avoid tissue response problems, and can beremotely actuated by using a very specific high-frequency signal (tag)transmitted by the external reader.

Miniaturization of the overall size and power consumption of thewireless implantable drug delivery device according to the presentdisclosure allows controlling the precise location of the drug delivery,targeting specific localized areas within a body. As a result, areduction of the overall quantity of dispensed chemistries is possible,which can therefore avoid many of the toxic side-effects often foundwhen potent medications are injected without much control.

The implantable drug delivery device according to the present disclosurecan be used to address the specific problem of treatment of brain tumorsthrough chemotherapy. As the blood-brain barrier often prevents the useof chemotherapy for treatment of brain tumors, the remote controlfeature over time and location of treatment provided by the implantabledrug delivery device according to the present disclosure can be a usefultool serving a critical and presently unmet medical need. When coupledwith the sensing feature described in the above Exemplary Case 1,on-chip measurements can further trigger/control the delivery ofmedications by the implantable drug delivery device.

In the following sections a wireless implantable drug delivery deviceaccording to the present disclosure is discussed, which can be furtherfitted with sensors. The electronic components of such system, asdepicted in FIG. 24, are similar to the electronic components depictedin the system of FIGS. 13 and 23, and include a wireless communicationinterface (labelled RX PWM-ASK 900 MHz), a wireless power deliverysystem (labelled Power Management Unit), and an actuation system(labelled Actuator) to open the hermetic package that contains amedication to be delivered (labelled Payload/Medication). To avoiddeleterious side-effects when these electronic components interact withthe surrounding tissue and/or the medication to be delivered, suchcomponents are encapsulated in an encapsulation chemistry (not shown).Similar electronic components of FIG. 24 to ones of FIGS. 13 and 23 havesimilar functionalities as described with reference to latter figures.

FIG. 25 shows a simplified cross section of the wireless implantabledrug delivery device according to the present disclosure. As can be seenin FIG. 25, the implantable device comprises a silicon substrate uponwhich the electronics components discussed with respect to FIG. 24 arefabricated. The silicon substrate further serves as a base to thehermetic package that contains the medication. Adhesive strips arefurther used to fixate the hermetic package upon the silicon substrate.A large side of the wireless implantable drug delivery device shown inFIG. 25 has a size of 1 mm or less.

With reference to FIG. 25, the hermetic package of the wirelessimplantable drug delivery device of the present disclosure can be madein many materials as well as geometries. Some such materials can beinjection molded polymers, micro-machined silicon, artificial foams orbubbles, hollow microbeads and even “smart” composites, all known to aperson skilled in the art.

According to an exemplary embodiment of the present disclosure, thehermetic package (delivery module) can be made to contain 1 microliterof chemistry (medication), which therefore provides a bottom limit ofthe delivery module size on the order of 1×1×1 mm. A person skilled inthe art knows of manufacturing techniques that can provide non-cubicdelivery geometries, which can therefore allow various shapes for thedelivery module. According to some exemplary embodiments of the presentdisclosure, the delivery module shape is an asymmetric “can” or a fullysymmetric sphere. According to further exemplary embodiments, severalsuch delivery modules, either of a same size or of different sizes, areprovided in the wireless implantable drug delivery according to thepresent disclosure so as to allow delivery of different dosages atdifferent times. Such delivery modules can be activated via differentactuators and therefore used at different times.

One challenge of drug delivery is the problem of filling the deliverymodule with reagent (e.g. medication) and subsequently sealing themodule without compromising the chemical potency of the reagent.Conventional sealing techniques known to a person skilled in the art,such as heat treatment to cure glues or to harden epoxies, maydeteriorate the reagent (medication), especially if delicatebiomolecules are to be delivered. Moreover, if the reagent is in liquidform, it is impossible to use most vacuum sealing technologies. Even thedevelopment of methods for filling medication into the small desiredgeometries (of the delivery module) within a reasonable timeframe can bevery challenging.

Alternatively, and in order to overcome the above shortcomings of theconventional sealing techniques, sealing of the delivery moduleaccording to the present disclosure can be provided by thermal settingof glues through local heating of the seal, UV-setting polymer basedadhesives that can be hardened by irradiating ultraviolet light ontothese polymers, or room-temperature setting glues. In such situations,MEMS type technology can provide small valves to be able to fill apre-sealed delivery module through the small valves. FIG. 25 shows anadhesive which can provide the sealing of the delivery module.

Quality of the seal used for sealing of the delivery module according tothe present disclosure can be remotely affected (controlled) by eitherheating or applying pressure onto the seal. On previous occasions,microfluidic devices have been constructed with paraffin or otherlow-temperature materials that were heated through local resistiveheating with a circuit that delivers a short pulse of high current or apulse of laser light. This heat pulse is applied to melt the paraffinand provide a leak for the medication in the package to diffuse into thesurrounding tissue. When translating this concept into wirelessimplantable devices that must function in-vivo, care must be taken toshrink the sizes of the heaters to reduce the overall power consumptionof the device while eliminating any possible overheating of thesurrounding tissue.

According to an embodiment of the present disclosure, a same structureof the wireless implantable drug delivery device is used to provide thefunctionalities of (a) a heater, (b) an antenna and (c) an actuationresistor. For these purposes, the heater can be constructed as a coil onthe outside of an electronics chip as shown, for example, in FIG. 19(4-turn coil), where the chip, positioned in the inside of the coil,comprises the electronic components discussed above with respect to FIG.24. Based on the relative positioning of the coil and the chip, the coilcan provide local heating of the rim of the chip. This is shown in FIG.25 where the antenna/heater/actuator is positioned in an outside area ofthe power/communication/actuation electronics (chip) at the vicinity ofthe adhesive which seals the delivery module.

With further reference to the sealing provided by the adhesive as shownin FIG. 25, in order to generate a high enough current pulse forsignificant heating of the antenna/heater/actuator, it may be necessaryto define a large capacitor on-chip that can be charged slowly over timeand discharges through the resistive heating geometry of the coil thatforms the antenna/heater/actuator. The coil can be designed to maximizeboth resistive and eddy current losses to maximize heating and minimizethe required power.

According to a further embodiment of the present disclosure, thermalactuation to affect the sealing of the delivery module is provided by ashape memory material, in which temperature pulses induce a phasetransformation in the memory material, and consequently high pressurewhich can rupture the seal.

According to some embodiments of the present disclosure, the pressureused to rupture the sealing of the delivery module can be generated bygas obtained through an electrochemical reaction, as shown in FIG. 26.In particular, as known to person skilled in the art, theelectrochemical dissociation of water from H₂O into its constituents,released as gaseous hydrogen and oxygen, requires 0.83+1.23=2.06 Voltsto occur, as governed by the following reactions and associated energy:

2H₂O+2e⁻→H₂+2OH⁻ requiring an energy: [E⁰=−0.83V]

2H₂O→O₂+4H⁺+4e⁻ requiring an energy: [E⁰=−1.23V]

where the number of molecules that are dissociated depends on theapplied current according to Faraday's laws, and each dissociation eventproduces one molecule of hydrogen and one half of an oxygen molecule.

With reference to FIG. 26, a person skilled in the art can recognize anelectrochemical cell that facilitates the dissociation of water into itsconstituent elements per the above electrochemical reactions. Hydrogenis generated at the cathode and oxygen is released at the anode. Inlarge volumes, this electrochemical process produces only small amountsof gas and insignificant pressure changes, but in confinedmicrogeometries such as the delivery module used in the wirelessimplantable drug delivery device of the present disclosure, hydrogenevolution can lead to very rapid pressure changes of up to 3 atmospheresper second pressure increase.

With further reference to the electrochemical dissociation reactiondepicted in FIG. 26, efficiency of the dissociation reaction can beincreased by using a solution (electrolyte) between the electrodes withreasonably low resistance which can therefore promote increasedconduction. In the case of the wireless implantable drug deliverydevice, increased conduction of the encapsulated chemistry(drug+electrolyte) can be obtained by using a liquid form of thechemistry with presence of salt or other ions in the chemistry so as topromote conduction. In some cases, the drug to be delivered may be ableto be mixed in an electrolyte solution without losing its efficiency,hence simplifying system design. This also allows using otherdissociation reactions at lower potentials to create other gases (e.g.chlorine) to create internal pressures which can rupture the sealing ofthe delivery module. The small quantity of gases generated by suchelectrochemical reaction can be within the safety and irritation limitsand not harmful to tissue surrounding the implantable delivery device.

The encapsulated chemistry needs to be appropriately designed to berobust with respect to the electrochemical requirements of the actuationmechanism. In other words, the mixture of the electrolyte and the drugto be delivered needs to produce enough pressure to cause rupture of theseal while using the smallest amount of electrolyte so as to keep theefficiency of the drug to be delivered. This is not always feasible. Itfollows that according to further embodiments of the present disclosurea two-chamber configuration is used for the wireless implantable drugdelivery device, where the electrolyte used for the electrochemicalreaction and the drug to be delivered are contained in separatechambers. In such a two-chamber system, the electrochemical reaction cantake place in a chamber next to the chamber containing the payload (drugto be delivered), with the sole purpose of rupturing the seal to allowdispensing of the payload as shown in FIGS. 27A and 27B.

Power generation for wireless implants often limits the minimum size ofsuch devices. Batteries can be deployed to power such devices, but theseare bulky, must be eventually replaced and often lead to toxicityconcerns. Supercapacitors offer a short-term alternative but must becharged with some method. If battery power is to be avoided, twopossible power generation methods for implants are 1) photovoltaicon-chip power generation along with infrared (remote) laser power fromthe reader, as described, for example, in the above referenced US PatentPublication No. 2014/0228660, herein incorporated by reference in itsentirety, and 2) microwave inductive coupling between coils in thereader and the implant as described above in relation to FIGS. 13, 23and 24. Remote optical powering from the reader can limit the locationof the implants to within less than 5 mm from the surface of the skin,as deeper implants require dangerously high power densities irradiatedthrough the skin, and therefore pulsed power approaches may be used forimplants located farther than 5 mm from the surface of the skin.Inductive coupling can enable deeper implant depths, depending on thetissue absorption of the microwave frequencies used. Formillimeter-sized devices, such as the wireless implantable drug deliverydevice of the present disclosure, a desired frequency is 900 MHz, whichmatches much of the cellphone technology and provides a depth ofcommunication and powering of approximately 1 cm into human tissue. Amajor advantage of microwave powering is the ease with which it can beintegrated with standard CMOS electronics, whereas the most importantadvantage of optical power transfer is the smaller size of the implantenabled by eliminating the need of antennas that have to approximatelymatch the wavelength of the powering radiation.

FIG. 28 shows a simplified top view of a wireless implantable drugdelivery device according to an embodiment of the present disclosurecomprising elements discussed above, including a silicon substrateserving as a base to the implantable device, an electronic chipcomprising circuitry to implement the various electronic componentsdiscussed with respect to FIG. 24, an antenna/heater/actuator elementformed at a periphery of the implantable device serving as coils for theinductive coupling between the implantable device and a correspondingreader/controller, and a dual chamber hermetic package which containsthe medication to be delivered and an electrolyte solution in separatesealed chambers. The sealed chamber containing the electrolyte alongwith the coil used as conductors to provide the functionality of theelectrochemical cell discussed in relation to FIG. 26, can cause theabove discussed electrochemical reaction to generate gases at highpressure that can rupture the seal and therefore allow the medication inthe second sealed chamber to be released in surrounding tissue, asdescribed in relation to FIGS. 27A and 27B.

FIG. 29 shows a simplified top view wireless implantable drug deliverydevice according to a further embodiment of the present disclosure,where a single sealed chamber is used to contain the medication to bedelivered. Rupturing of the seal to dispense the medication is performedvia heating of the seal provided by the antenna/heater/actuator elementas discussed above in relation to FIG. 25. Other elements of theimplantable device depicted in FIG. 29 are similar to the elementsdiscussed in FIG. 28.

With further reference to the wireless implantable drug delivery devicedepicted in FIGS. 28 and 29, actuation of the implantable device thattriggers dispensing of the medication is only possible throughelectronic control via an external reader/controller (keyed/locked tothe implantable device) and therefore inadvertent leaks of thepayload/medication are avoided. A remote signal generated by theexternal reader/controller actuates the CMOS electronics chip which inturn starts an electronic process of generating enough energy to releasea pulse of either heat (e.g. FIG. 29) or pressure (e.g. FIG. 28) to openleakage paths through which the payload can be dispensed. Furtherdetails of the actuation, including techniques for storage of energy forproviding such pulses in a capacitor bank for later discharge, can befound in the above description as related to the actuator of FIG. 23.

The wireless implantable drug delivery device according to the presentdisclosure uses carefully selected materials that can withstand thecorrosive in-vivo environment that the implantable device is subjectedto for long time periods while reducing the effect of the implant on thesurrounding tissue. These can be biocompatible materials, including andnot limited to materials such as silicones, polyurethanes, poly vinylacetate (PVA), etc. Furthermore, some possible (non-limiting) adhesivescan be, for example, USP Class VI adhesives (e.g. from Masterbond). Aperson skilled in the art would know of other biocompatible materials tobe used in the wireless implantable drug delivery device according tothe present disclosure.

With further reference to the wireless implantable drug delivery deviceaccording to the present disclosure, the single/dual chamber used tocarry the drug to be delivered, and optionally the electrolyte, can, asdiscussed above, be bonded to the silicon substrate of the implantabledevice. According to some embodiments of the present disclosure, thechamber can either be a self-contained silicon-on-insulator (SOI)chamber, a micro-machined fluidic chamber as provided in a fluidicsystem, or a filled cup whose rim can be bonded to the silicon coversurface (FIGS. 25, 27A, 27B), all of which are known to a person skilledin the art.

As discussed above, the wireless implantable drug delivery deviceaccording to the present disclosure can be fitted with sensors similarto sensors used in the above discussed wireless implantable sensingdevice with minimal impact on the size of the combined device as sameelectronic components can be used for both actuation of the sealedchamber and sensing (e.g. see circuits of FIGS. 13, 23 and 24).Electronic components of such system are depicted in FIG. 30 anddescribed in the above description as related to FIGS. 13, 23 and 24. Byvirtue of being fitted with electrochemical sensing capability, theimplantable device according to the present disclosure can perform thetask of dispensing the medication based on sensed species. According tofurther embodiments of the present disclosure, an amount of thedispensed medication can be a function of a measured concentration ofsensed species. By providing a plurality of chambers of known volumetricsize containing a medication to be delivered, seal of one or more ofsuch chambers can be ruptured by way of techniques (heat, pressure)described above based on the measured concentration. A corresponding topview of such implantable device is shown in FIG. 31, which shows fourchambers mounted on areas comprising the coils of theantenna/heater/actuator element, and a sensor (with correspondingelectrodes) mounted in the central area of the implantable device atopthe electronics chip. A person skilled in the art would know of otherpossible layouts of the implantable device according to the presentdisclosure, and therefore the exemplary layouts shown in the variousfigures (e.g. 25, 27A, 27B, 28, 29 and 31) should not be considered aslimiting the scope of the present invention. The person skilled in theart would use the various principles of operation, including actuation,interface, powering, sensing and dispensing as described above inimplantable devices having different layouts than ones described above.In particular, size and positioning of the chamber containing themedication to be delivered may vary as best suited for a givenapplication.

The wireless implantable devices described in the present disclosure canbe used for continuous in-vivo monitoring of disease biomarkers andtreatment efficacy and for telemetric delivery of therapeutic reagentswith spatial and temporal control. Prior art efforts to continuouslymonitor analytes in-vivo follow a strategy of copying establishedin-vitro approaches such as binding chemistries, enzyme electrochemistrymeasurements, or hybridization sensing. However, such traditionalapproaches have known shortcomings, such as (a) limited lifetime of thedevices as the surface functionalization coating deteriorates with time,(b) lack of specificity resulting from the extreme complexity of mostbody fluids compared to benchtop laboratory testing systems wherefiltration and pre-concentration of such body fluids is possible, and(c) the need to clean the surfaces periodically to avoid bio-fouling.Moreover, there are only a few chemistries that have been demonstratedfor stable measurement of a limited set of analytes, such as glucose orlactate. As known to a person skilled in the art, glucose oxidase ordehydrogenase, for example, converts glucose to gluconic acid andreleases a hydrogen peroxide ion in the process that can functionin-vivo for approximately three weeks, mainly as a result of enzymedegradation. In particular, binding reactions can be problematic tomonitor over long periods of time in-vivo, since the functionalizedmeasurement surface must be periodically cleaned, requiring aptamers orother thermally stable chemistries to be deployed. In contrast, thecommonly used antibody binding assays for in-vitro tests require onlyone-time binding and no cleaning. Many interesting chemistries, such ascytokines (as inflammation indicators) or micro-RNAs (ribonucleic acid)cannot be readily measured because of a lack of specific surfacechemistry and their folded or sheathed geometries in exosomes.

In order to circumvent the above mentioned shortcomings with respect tothe traditional approaches for in-vivo monitoring of chemistries,methods according to the present disclosure monitor changes in in-vivochemistries with cell cultures or colonies that are selected to be verysensitive and specific to the analytes that need to be detected.Physiological characteristics and/or metabolic “wellness” of these cellcultures or colonies can be in turn monitored with, for example, thewireless implantable devices of the present disclosure, or anyconventional electrochemical micro-sensors that can measure stable ionor analyte concentrations, or even light from fluorescence generated byred or green fluorescent proteins (GFP).

Methods according to the present disclosure for in-vivo monitoring ofchemistries can allow measurement of the metabolic reaction of thecultured cells to the analytes of interest. One of the key advantages ofthis approach stems from the ability of such a biological interfacebetween the cultured cells and the analytes to unfold and recognize (viaintegrated sensors) molecules that are typically folded, such ascytokines or even exosomes, tasks that are exceedingly difficult withcurrent hardware and methods of use. For example, specifically selectedcell colonies can sense genomic markers like micro-RNAs or circulatingDNAs, exosomes and cytokine molecules in blood, interstitial fluid,urine or saliva. Moreover, it is not necessary to continuously cleansurface contacts from bio-fouling products if the cell colonies andmetabolic measurements are carefully selected.

In an exemplary case of the in-vivo monitoring methods according to thepresent disclosure, fluorescent protein markers are used and acorresponding optical signal can be recognized (e.g. via optical sensorin an implantable device) without the need of any open electrodesurfaces, therefore rendering cleaning of surface coatings unnecessary.An implanted wireless device fitted with an optical sensor can detectfluorescence emitted by the fluorescent protein markers that reactedwith an analyte. An exemplary case of such implantable wireless deviceis described, for example, in US Patent Publication No. 2014/0228660entitled “Miniaturized Implantable Electrochemical Sensor Devices”,published Aug. 14, 2014 which is herein incorporated by reference in itsentirety.

In yet another exemplary case of the in-vivo monitoring methodsaccording to the present disclosure, health (“wellness”) of cells can beobserved/monitored by measuring ions or body gases (pH, NO, CO, O2etc.). Such in-vivo monitoring simply requires ion membranes andionophores for selectivity, and does not require enzymes or surfacecoatings that could deteriorate with time.

As mentioned above, the in-vivo monitoring methods according to thepresent disclosure can use the minimally invasive wireless implantabledevices of the present disclosure to take advantage of the built inelectrochemical measurement capabilities as well as the built in drugdelivery capabilities. The built in micro-sensors monitor the responseof cells (that take the place of canaries in coal-mines) to the specificanalytes. The in-vivo lifetimes of these wireless implantable devices isexpected to outpace modern analyte detection for months to years withoutthe risk of infection.

According to a further embodiment of the present disclosure, an in-vivobio-electronic system is presented which can monitor the health of cellcolonies or cultures and accordingly dispense corresponding therapeuticdrugs. Such in-vivo bio-electronic system comprises cellular interfacesformed by cells that are sensitive to specific chemistries, and awireless implantable device of the present disclosure containingtherapeutic sources (drugs) that can be used to produce in-vivo localtherapy of the cells in response to sensed reactions, by the implantabledevice, of the cellular interface. According to further embodiments ofthe present disclosure, the in-vivo bio-electronic system is protectedby a semi-permeable cell containment barrier, such as an organic pouchor parylene, as shown in FIG. 32.

According to one exemplary embodiment of the present disclosure, thecells of the in-vivo bio-electronic system are genetically engineeredcells, designed, for example, for longevity and selectivity to specificmolecules (e.g. cytokines, microRNAs, etc.). The in-vivo bio-electronicsystem according to the present disclosure, can therefore integrate CMOSsensor “intelligence” with genetically engineered cells that producein-vivo local therapy on demand. Such closed-loop, in-vivobio-electronic system of the present disclosure, can therefore resembleto an “artificial organ” in which disease measurement and therapeuticdrug production are combined.

According to a further exemplary embodiment of the present disclosure,the in-vivo bio-electronic system according to the present disclosurecomprises the wireless implantable device of the present disclosurefitted with sensors (functionalization layer) that can trackphysiological changes of indicator cell colonies in response to chemo-or immuno-therapy. Accordingly, the wireless implantable device canmonitor and control indicator cell colonies by first detecting aninflammation, and then delivering a local therapy (dispensing drug).Such hybrid biological/electronic monitoring system can thereforeresemble to an “artificial organ” remotely controlled through aconventional (e.g. CMOS) electronic interface.

The above methods and systems using the wireless implantable device ofthe present disclosure are transformative and can overcome some of themajor impediments in preventive healthcare by developing minimallyinvasive implants to more efficiently monitor and treat many chronic andinflammatory disorders with long lifetimes.

Teachings according to the various embodiments of the present disclosurecan be used for other applications related to implants by changing, forexample, a corresponding system configuration. As noted in priorsections of the present disclosure (e.g. functionalization versatility),functionalization chemistry can be changed according to a desiredsensing application, such as, for example, using urease instead ofglucose oxidase to sense urea. The person skilled in the art can findnumerous other examples while taking advantage of the present teachings.

A number of embodiments of the disclosure have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the presentdisclosure. Accordingly, other embodiments are within the scope of thefollowing claims.

The examples set forth above are provided to those of ordinary skill inthe art as a complete disclosure and description of how to make and usethe embodiments of the disclosure, and are not intended to limit thescope of what the inventor/inventors regard as their disclosure.

Modifications of the above-described modes for carrying out the methodsand systems herein disclosed that are obvious to persons of skill in theart are intended to be within the scope of the following claims. Allpatents and publications mentioned in the specification are indicativeof the levels of skill of those skilled in the art to which thedisclosure pertains. All references cited in this disclosure areincorporated by reference to the same extent as if each reference hadbeen incorporated by reference in its entirety individually.

It is to be understood that the disclosure is not limited to particularmethods or systems, which can, of course, vary. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting. As used in this specification and the appended claims, thesingular forms “a,” “an,” and “the” include plural referents unless thecontent clearly dictates otherwise. The term “plurality” includes two ormore referents unless the content clearly dictates otherwise. Unlessdefined otherwise, all technical and scientific terms used herein havethe same meaning as commonly understood by one of ordinary skill in theart to which the disclosure pertains.

LIST OF REFERENCES

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1. A method for fabricating a miniaturized implantable device:fabricating an electronic system by monolithically integrating theelectronic system on a first face of a substrate, the electronic systemcomprising an energy storage element adapted to be charged through awireless communication link; fabricating a coil by monolithicallyintegrating the coil on the first face of the substrate, the coil beingconfigured to provide the wireless communication link; and fixating atleast one hermetic package, containing a liquid payload, on the firstsurface of the substrate, a portion of the hermetic package beingpositioned above the coil, wherein the energy storage element isconfigured to provide energy to rupture a seal of the hermetic package,thereby dispensing the liquid payload.
 2. The method according to claim1, wherein the rupture of the seal is provided by applying heat to theseal.
 3. The method according to claim 2, wherein the heat is providedby injecting current in the coil, the current provided by the energystorage element.
 4. The method according the claim 1, wherein therupture of the seal is provided by applying internal pressure to thehermetic package.
 5. The method according to claim 4, wherein theinternal pressure is provided by gases released through anelectrochemical dissociation reaction of an electrolyte solutioncontained in the hermetic package, energy for the electrochemicaldissociation being provided by the energy storage element.
 6. The methodaccording to claim 5, wherein the hermetic package comprises one chambercontaining a mixture of the electrolyte solution and the liquid payload.7. The method according to claim 5, wherein the hermetic packagecomprises two separate chambers, a first chamber containing theelectrolyte solution and a second chamber containing the liquid payload.8. The method according to claim 1, further comprising: fabricating aplurality of electrodes of an electrochemical sensor by monolithicallyintegrating the plurality of electrodes on the first face of thesubstrate, the plurality of electrodes being configured to provideelectrical interface between the electrochemical sensor of theimplantable device and the electronic system.
 9. The method according toclaim 8, wherein the fabricating the plurality of electrodes furthercomprises fabricating the plurality of electrodes on a first metal layerseparate from metal layers used to fabricate the electronic system. 10.The method according to claim 8, wherein the fabricating the pluralityof electrodes further comprises creating a plurality of wells incorrespondence of the plurality of electrodes.
 11. The method accordingto claim 1, wherein the energy storage element is a bank of capacitorscharged through power extracted from the wireless communication link.12. The method according to claim 1, wherein the fabricating of the coilcomprises fabricating a plurality of concentric patterns on a firstmetal layer separate from metal layers used to fabricate the electronicsystem.